N12WB

The pilot reported that prior to the takeoff roll, his son, who was positioned in the front right seat, had difficulty shutting and locking the cabin door. The pilot reported that he reached over and ensured the door was locked.

The pilot reported that shortly after liftoff the cabin door came open. He maneuvered the airplane to stay in the traffic pattern and return to land. He reported that while on final he did not have any rudder authority and was unable to keep directional control. The pilot reported that prior to the initial impact he lost sight of the runway when the airplane pitched up and rolled left simultaneously. Subsequently the left wing impacted the ground and sustained substantial damage.

The cabin door is hinged in the front and secured at the top, bottom, and aft edge when closed and locked. A post-accident examination of the door by the National Transportation Safety Board investigator-in-charge revealed that the lower striker plate, which secures the bottom of the door to the doorframe, had screw holes that were elongated inward about 1/8 of an inch from their original position, resulting in a misalignment. The two screws that attach the striker plate to the airframe were in place, and the striker plate was secure. The striker plate on the bottom of the cabin door frame acts as a guide for the latch pin to secure the cabin door to the airframe when in the closed and locked position. The upper and aft locking points were examined and no deficiencies were found.

According to the manufacture, if the latch pin cannot extend though the striker plate, the door will be difficult to latch, and the unresolved displacement of the lower latch pin can cause feedback in the door latching system that may result in the entire latching system unlatching.

According to the manufacture, a mandatory service bulletin (No. 2457, Rev. 1) was issued September, 1993 and revised February 1994. The service bulletin was issued to "provide cabin door third latch pin over-center mechanism kits that will reduce the possibility of a cabin door opening in flight." The accident airplane was not in compliance with the service bulletin.

The following procedure that is listed in the airplane's Owner's Manual should be used for an unlatched door in flight. "If the cabin door is not locked it may come unlatched in flight. This usually occurs during or just after takeoff. The door will trail in a position 3 to 4 inches open, but the flight characteristics of the airplane will not be affected. Return to the field in a normal manner".